Some portable devices comprise integrated speakers for creating sound such as playing back music or having a telephone conversation. The loudness of the integrated speakers is important especially in environments where the ambient noise levels are high, even indoors. The loudness of the integrated speakers in a portable device is important for perception of ringtones of a mobile telephone. In some countries the loudness of the integrated speakers is important for listening to radio broadcasts.
In some parts of the world a portable device with an integrated speaker may be the only device the user owns which is capable of playing music. For example, a user may only be able to play music using a loudspeaker of a mobile telephone. The loudness and quality of sound from an integrated speaker is even more important if a user is solely reliant on an integrated speaker of a portable device for music playback.
It is known to increase the loudness of integrated speakers by actively amplifying sound by electronic solutions. For example, circuitry comprising large transducers, components for signal processing and other electrical modifications have been used. Other solutions further comprise external loudspeakers. Typically digital signal processing (DSP) may increase loudness by using one or more of the following; digital gains, equalization (EQ), single or multiple dynamic range controllers (DRC) and transducer protection. It is understood that there may be more additional systems or algorithms which are designed for use in digital signal processing. For example, in addition there may be and/or other systems in a playback chain such as electrical filters.